Technical seminar on recycling of waste tyre rubber into sustainable low-noise rubberised asphalt pavement
By Mr Kenny CHAN

If you choose to listen to this article, you are welcome to download the PDF version of the Journal (January 2022 issue) and activate the “Read Out Loud” function in Adobe Reader. For more details, please read the user's note.


The captioned webinar was presented by Dr Zhen Leng, an Associate Professor of Civil and Environmental Engineering at The Hong Kong Polytechnic University, where he also serves as the Director of the Road Research Laboratory. His research interests mainly include sustainable infrastructure materials and technologies, eco-efficiency analysis and life cycle assessment, and non-destructive evaluation of transportation infrastructure.


Dr Leng started the seminar by illustrating the significance of applying low-noise rubberised asphalt technologies on pavements in Hong Kong. Rapid urban development and an increasing population in Hong Kong are making traffic noise a noticeable issue. Noise barriers, while widely adopted locally as a countermeasure are bulky, expensive, and disturbing to road users. Low noise road surfacing (LNRS) is therefore the preferred option on many occasions.


Dr Leng then introduced waste tyre rubber as one of the preferred materials for surfacing, as it can enhance the mechanical performance of pavements and reduce tyre-road noise. At the same time, while waste tyre rubber is non-degradable, there were more than 20,000 tons of waste tyres disposed in landfills in 2019, with a recycling rate of only around 30%. Applying waste tyre rubber in pavements is therefore considered a value-added recycling approach. However, rubberised asphalt had not been practically adopted for environmental concerns, in terms of emissions and odour.


Dr Leng continued by presenting a technical breakthrough: warm-mix asphalt (WMA), which would alleviate the environmental concerns. WMA reduces construction temperatures by at least 16°C while achieving similar performance to traditional hot-mix asphalt (HMA) by applying additives, so that emissions and odour can be reduced. Their research found that Sasobit, a wax additive, is the best performing option for WMA.


The research team conducted a field trial at Fo Tan Road in June 2017, which compared original SMA201 pavement without crumb rubber to a newly applied warm ARSMA62. It resulted in a positive outcome. Air samples collected during construction demonstrated satisfactory odour and emission levels, while the tyre-road noise of the warm ARSMA6 was 4 dB lower than existing SMA20.


On behalf of the CV Division, we would like to express our sincere thanks to Dr Leng for his insightful presentation. More than 400 members attended the webinar.


  1. SMA20: 20 mm stone mastic asphalt (SMA) mix
  2. ARSMA6: 6 mm SMA mix with 18% crumb rubber and 3% Sasobit

Technical visit to first phase of Kwu Tung North New Development Area
By Mr Matthew C K LO

If you choose to listen to this article, you are welcome to download the PDF version of the Journal (January 2022 issue) and activate the “Read Out Loud” function in Adobe Reader. For more details, please read the user's note.


The Government’s latest announcement on the blueprint for the Northern Metroplis, Kwu Tung North New Development Area (KTN NDA), presents this as one of the major mixed land use development projects providing for residential, commercial, research and development, and agricultural use for natural and ecological conservation.


The CV Division organised the captioned visit to the First Phase of the Development on 4 December 2021. The event included a brief visit to the Arsenic Treatment Plant, the Service Reservoirs, and the Long Valley Nature Park (LVNP).


Soil found at KTN NDA contains high concentrations of arsenic. Under the approval conditions of the Environmental Impact Assessment Report, a football-field-sized soil treatment plant was built to address the problem. Cement stabilisation was arranged for backfilling use in the site formation works.


The treatment plant also adopted several environmental mitigation measures, including reusing grey water to minimise public disturbance.


Our second destination was one of the key infrastructure projects of KTN NDA –service reservoirs. Extensive foundation work and slope improvement work at the uphill site location were also demonstrated.


The last destination was the LVNP site, which is known as the largest contiguous freshwater wetland in Hong Kong and is one of the rarest and richest ecosystems for diverse wildlife in the territory.


Representatives from the Conservancy Association and Hong Kong Bird Watching Society demonstrated how the ndevelopment of LVNP had enhanced the habitat for wetland species.


On behalf of the CV Division and participants, we would like to express our sincere thanks to AECOM Resident Site Staff (RSS), along with the contractor’s representatives from Build King – Richwell Engineering Joint Venture and Sang Hing – Kuly Joint Venture. They delivered a fruitful and knowledgeable presentation on the implications of smart engineering measures in environmental conservation on the KTN NDA project. Through this visit, participants not only had a better understanding of the new development in Kwu Tung but could also witness the environmental diversity in Hong Kong and the environmental sensitivity of the Hong Kong construction professions.

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